The Tonga-born prop agreed a deal to remain with the Queensland Super Rugby franchise and continue to be available for the Wallabies until after the 2023 Rugby World Cup in France.
Tupou has won 13 caps for Australia since making his debut against Scotland in 2017, having made a big impact with the Reds after joining them straight from high school five years ago.
The 23-year-old said: "I'm very excited to sign for the next few years. Queensland and Australia offered me the first opportunity out of school and I feel I have more to do to repay that faith.
"I only started playing consistently in the last two or three years, so I think there's still more for me to offer in Australia for the Reds and Wallabies.
"We have a really good young group in Queensland who have been working hard the last few years and I know we're heading in the right direction.
"I love playing for Australia. Obviously growing up as a kid, watching them, and now being able to pull on the jersey is an honour. To know that I will be here for the next four years is exciting because it means I may have the opportunity to pull on the jersey again if I continue to work hard."
Reds head coach Brad Thorn said: "It's good to see Taniela Tupou re-commit to Queensland.
"To have him here at Ballymore for the next four years is a great result. He's come through the system with the Queensland U20s and is only four caps away now from playing 50 games for Queensland.
"Taniela's developed a lot since he arrived at Ballymore as an 18-year-old. He's a threat to any opposition. He's a strong ball runner and is even tougher in defence. With more hard work he can only better."